Ok, I have a question. I hear a lot about "tipping point". Isn't it true that in the long run, we saw dramatically higher CO2 concentrations than on your 300 year time scale? Didn't we see a long-term downward trend in CO2? Doesn't this suggest there's not an "irreversible tipping point"? Or are you, too, cherry picking a time scale shorter than the one I'm now using? That's one of the things I'm having a really hard time accepting, because while I can absolutely see a modest increase in temperature due to anthropogenic CO2 emissions, I cannot for the life of me understand the "tipping point" argument, which we head a lot of when we accept reaonable conservative estimates of temperate shifts due to man made CO2 emissions.